Fine sediment plays a key role in the transport of contaminants in rivers and the quantification of suspended sediment flux is important to understanding and managing river catchments in the context of the EU Water Framework Directive (2000/60/EC). Recent European studies identified Ireland as having a paucity of sediment and sediment associated pollutant concentration and flux data. This paper presents the results of a continuous monitoring programme on a small scale catchment (105 km 2 ) in Ireland, the River Owenabue, which is located in the South Western River Basin District. Analysis was undertaken to determine event based fluxes and their contribution to the annual flux.The continuous monitoring programme commenced in September 2009. Analysis shows that turbidity is an accurate surrogate for suspended sediment concentration for this river and when coupled to river flow data provides estimates of the suspended sediment flux. The objective of this paper is to quantify the suspended sediment flux of a small Irish River, and to analyse the dynamic delivery sequence of storm based events. The variation of the suspended sediment flux at different temporal scales is investigated and found to be significant.The annual suspended sediment flux was found to be 2635 tonnes (t) which equates to a suspended sediment yield of 25.6 t km -2 year -1 . The flux analysis reveals that 85% of the total annual flux is transported over 10% of the year and 69% of the flux over 5% of the year. return period flow rate of approximately 10 years, the flux is estimated at 38% of the annual flux. Hysteresis is observed and analysed for the identified events and it is found that clockwise hysteric loop are most common implying that suspended sediment transport is most commonly limited by sediment supply.
Abstract. The objective of this research was to investigate the relationship between water and sediment discharge on the transport of nutrients: nitrogen and phosphorus. Water discharge, suspended sediment concentration and dissolved and particulate forms of nitrogen and phosphorus were monitored on the 105 km 2 River Owenabue catchment in Ireland.Water discharge was found to have an influence on both particulate and dissolved nutrient transport, but more so for particulate nutrients. The particulate portion of N and P in collected samples was found to be 24 and 39 %, respectively. Increased particulate nitrogen concentrations were found at the onset of high discharge events, but did not correlate well to discharge. High concentrations of phosphorus were associated with increased discharge rates and the coefficient of determination (r 2 ) between most forms of phosphorus and both discharge and suspended sediment concentrations were observed to be greater than 0.5.The mean TN yield is 4004 kg km −2 yr −1 for the full 29-month monitoring period with a mean PN yield of 982 kg km −2 yr −1 , 25 % of the TN yield with the contribution to the yield of PN and PP estimated to be 25 and 53 % respectively. These yields represent a PN and PP contribution to the suspended sediment load of 5.6 and 0.28 % respectively for the monitoring period.While total nitrogen and total phosphorus levels were similar to other European catchments, levels of bio-available phosphorus were elevated indicating a potential risk of eutrophication within the river.
This paper presents aspects of sediment and nutrient behaviour on the River Bandon which is located in the South Western River Basin District in Ireland; it is a relatively large sized river catchment in an Irish context with a catchment area of 608 km 2 . The river catchment is primarily agricultural with some pockets of urban development. The river is prone to flooding on stretches, features a number of special areas of conservation and is distinguished by both suspended and bed load transport.Continuous monitoring of turbidity commenced in February 2010. Manual sampling and testing for suspended sediment concentration and a range of species of phosphorous was also undertaken. Analysis shows that turbidity is a suitable surrogate for suspended sediment concentration allowing suspended sediment loads to be analysed from the continuous data. Similarly suspended sediment concentration has been found to correlate well with total and particulate phosphorous allowing phosphorous loads to be analysed using the continuous data.The annual suspended sediment load was 6012 tonnes, with the highest loads experienced during the winter months. The annual total phosphorous load was found to be 42.9 tonnes with particulate phosphorous accounting for approximately 64% of this total. High flow storm based events contribute disproportionately to suspended sediment and phosphorous transport.The rating curve approach applied to the sampled data can provide good estimates of the annual load which has particular relevance to Ireland where the current database of suspended sediment information is limited.
Abstract. The objective of this research was to investigate the relationship between water and sediment discharge on the transport of enriching nutrients: nitrogen and phosphorus. Water discharge, suspended sediment concentration and dissolved and particulate forms of nitrogen and phosphorus were monitored on the 105 km2 River Owenabue catchment in Ireland. Water discharge was found to have an influence on both particulate and dissolved nutrient transport, but more so for particulate nutrients. The particulate portion of N and P in collected samples was found to be 24 and 39% respectively. Increased particulate nitrogen concentrations were found at the onset of high discharge events, but did not correlate well to discharge. High concentrations of phosphorus were associated with increased discharge rates and coefficient of determination, r2, between most forms of phosphorus and both discharge and suspended sediment concentrations were observed to be greater than 0.5. The mean TN yield is 4004 kg km−2 yr−1 for the full 29 month monitoring period with a mean PN yield of 982 kg km−2 yr−1, 25% of the TN yield. The contribution to the yield of PN and PP estimated to be 25 and 53% respectively. These yields represent a PN and PP contribution to the suspended sediment load of 5.6 and 0.28% respectively for the monitoring period. While total nitrogen and total phosphorus levels were similar to other European catchments, levels of bio-available phosphorus were elevated indicating a potential eutrophication risk to the river where phosphorus was found to be the limiting nutrient.
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